Manufacture of acrylic acid



Patented Jan. 7;

, lJNlTl-lD STATES PATENT OFFICE I 2,026,894

MANUFACTURE or scams ACID Rowland mu, Blachley. Manchester, England,assignor to Imperial Chemical Industries Limited, a corp ration of GreatBritain No Drawing. Application May 16, 1934, Serial No. 125,953. InGreat Britain April 13.1933

11 Claims. 260-112) The present invention relates to an improved methodfor the manufacture of acrylic acid.

It has previously 'been proposed to hydrolyze ethylene cyanohydrin withaqueous sodium hydroxide, isolate the sodium hydracrylate formed 2. In aprocess for theeproduction of acrylic 1 acid the step which comprisesheating ethylene cyanohydrin with is. sulphuric by evaporatingthesolution, heat the sodium hydracrylate acrylic acid by distillation withsulphuric acid (Van den Berg. Rec. Trav. Chim. 1922, 41, 22

According to the present invention, we make acrylic acid by treatingethylene-,cyanohydrin with sulphuric acid and water. The process issimple and the yield is good.

In carrying the invention in practical efiect,

' ethylene cyanohydrin, sulphuric acid and water may be mixed inproportions corresponding to a. sulphuric acidot about 80-96% H2804content, the mixture heated and the acrylic acid recovered from thecrystalline mush of ammonium bisulphate by solvent extraction, or bydistillation, distillation being preferably under reduced pressure. i

Antipolymerizing agents such as copper, hydroquinone, pyrogallol, tannicacid, diphenyl amine,

25 gand other active antioxidants are preferably inand a!ter remo'val 01the acetone.

trodiiced into the, reaction mixture in order to prevent polymerization,especially during a di'stil lation process.

The following. examples in which parts are by weight, illustrate butdo'not limit the invention; Emample1.98 parts of sulphuric acid (sp. gr.

1.84/20" C.) are added to '71 parts of ethylene cy anohydrin and 2 partsof copper toil with stirring during /2v hour, the mixture being cooledwith ice and salt. 18 parts of .water are then added and the mixturewarmed under reflux. At about 80 C. a fairly vigorous reaction begins.when heating should be stopped, and cooling eflected it necessary. Thetemperature may rise'to 130- 140 C.-but rapidly subsides. Heatingiscontinued ior 16 hours at .95" C. The semi-solid crystalline mass isextracted with 140 parts of acetone.

0.5 part of hydroquinone is addetPas stabilizer. 51 parts of acrylicacid b. p. 132-441 C. (chiefly 140 C.) can be isolated by fractionaldistillation.

EzampieL-llfi parts of sulphuric acid (sp.

gr. 1.11/20" 0.) are added to '11 parts or ethylene cyanohydrin and 2parts of copper. The mixture is then heated at 95 C. After 3 hoursammonium bisulphate starts to separate ,irom the reaction mixture. After18 hours, the whole is subjected tovacuum distillation under pressure01-30 mm. mercury. -54 parts of distillate are obtained, from whichacrylic acid can be isolated ina pure condition by iractionation. 1

I claim:

to eliminate water, and recover the acid 01 80-96% strength, l 1

-3. In a. process for the production er acrylic 5 acid the step whichcomprises heating ethylene cyanohygrin with sulphuric acid and water inthe presence of ,an antipolymerizing agent.

.4. In a process for the production of acrylic acid the step whichcomprises heating ethylene l0 cyanohydrin with a sulp uric acid or80-96% strength in the presence'oi an antipolymerizing agent.

' 5. In a process for the production of acrylic acid the step whichcomprises heating ethylene 1 cyanohydrin with sulphuric acid and waterin v the ,presence of an antioxidant.-

6. In a process for the production of acrylic acid the: step whichcomprises heating ethylene cyanohydrin with sulphuric acid and water inthe 5 acid the step which comprises reacting-ethylene cyanohydrin' withsulphuric acid and water in the 307 presence 0! hydroquinone.

9. In a process tor-the production of: acrylic acid the'step whichcomprises reacting ethylene H cyanohydrin with sulphuric acid and waterin the presence-of py allol. 3o

10. A process for the production of acrylic acid which comprises addingto a mixture containing and "stirred during the addition, adding waterto an antioxidant and ethylene cyanohydrin concentrated sulphuric acid,the mixture being cooled the resulting mixture, heating until thereaction is initiated, stopping theinput 01 heat until the vigorousevolution or exothermic heat has subsided, and subsequently heating thereaction mixture until the reaction is substantially complete. o 11. A.process for the-production of acrylic acid which cdmprises adding to amixture containing approximately 2 parts of copper toil and approx--imately '11 parts of ethylene'cyanohydrin, about I 98 parts-o1concentrated sulphuric acid, the mixtwo being stirredand cooledduring'theaddi- I tion 0! the concentrated sulphuricacid, adding waterto the resulting mixture, heating to approximately C., and alter thevigorous reaction has subsided, v approximately 0.; for about 16 hours,and sub:- separating the acrylic acid byextrac 1. ms process'icr isproduction or acrylic no -end iractionjal distillation;

acid the step which comprises, heating eti i ene maintaining thetemperature at 55

